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Acidic hot water flowthrough pretreatment (AHWF) is an attractive approach primarily because of its high efficiency for sugar recovery. However, a significant portion of carbon content in the solubilized fractions from lignin depolymerization and monosugar degradation has been studied to a lesser degree. Herein, we investigated the solubilized non-carbohydrate products from a series of flowthrough pretreatments of poplar wood by water-only or very dilute acid (0.05% to 0.1% w/w, H2SO4) at different temperatures (220 to 280 °C) and flow rates (10 to 62.5 mL/min). Results revealed that tailoring reaction parameters (temperature) and operational parameters of reactor (flow rate) without adding expensive catalysts can selectively produce specific non-carbohydrate compounds. Up to 50.9% selectivity of vanillin and 45.0% selectivity of syringaldehyde were obtained at 240 °C for water-only treatment with flow rates of 25 mL/min and 62.5 mL/min, respectively. Lower temperature (e.g., 220 °C) was favorable for the formation of coniferyl alcohol, with the highest selectivity of 36.2%. Higher temperature (e.g., 280 °C) or lower flow rate (e.g., 10 mL/min) led to the formation of varied other aromatic compounds and HMF. Adding very dilute acid (0.05% to 0.1% w/w, H2SO4) into the water-only system considerably enhanced the formation of HMF with up to 66.7% selectivity.

This paper describes in detail a novel formulation of the method of characteristics for its application to solve one-dimensional compressible unsteady non-homentropic flow advected along porous wall channels. In particular, the method is implemented into a wall-flow monolith Diesel particulate filter model whose purpose is the pressure drop prediction. The flow inside the monolith channels is considered to be one-dimensional and the flow through the porous wall treated as a source term agree with the Darcy's law. The flow dynamic behaviour at internal nodes of the channels is solved by means of shock capturing methods, whereas the end nodes, or boundary conditions, are solved applying the method of characteristics. The derived solution in this study of the Riemann variables and the entropy level includes the variation along the space-time plane due to cross-section area changes, friction and heat transfer as traditionally stated, but also takes into account the key influence on every line of the flow leaving or entering to the channels through the porous walls. © 2011 Elsevier Inc.

This present paper describes three dimensional computational analysis of complex internal flow in a cross flow fan, (CFF) with a special emphasis on the performance improvement by varying impeller and casing geometries, inlet and tongue clearance gaps. RNG k-? two-equation turbulence model is used to simulate the model with unstructured mesh. Sliding mesh interface is used at the interface between the rotating and stationary domains to capture the unsteady interactions. Three impeller geometries, seven casing configurations and three inlet and tongue clearances are varied in the present study. The efficiency of the fan has improved from 59 % to 71 % and that of casing from 37 % to 61 %. Maximum energy transfer through the impeller takes place in the region where the flow follows the blade curvature. � 2012 Begell House, Inc.

A thin film of a power-law fluid flowing down a porous inclined plane is considered. It is assumed that the flow through the porous medium is governed by the modified Darcy's law together with Beavers-Joseph boundary condition for a general power-law fluid. Under the assumption of small permeability relative to the thickness of the overlying fluid layer, the flow is decoupled from the filtration flow through the porous medium and a slip condition at the bottom is used to incorporate the effects of the permeability of the porous substrate. Applying the long-wave theory, a nonlinear evolution equation for the thickness of the film is obtained. A linear stability analysis of the base flow is performed and the critical condition for the onset of instability is obtained. The results show that the substrate porosity in general destabilizes the film flow system and the shear-thinning rheology enhances this destabilizing effect. A weakly nonlinear stability analysis reveals the existence of supercritical stable and subcritical unstable regions in the wave number versus Reynolds number parameter space. The numerical solution of the nonlinear evolution equation in a periodic domain shows that the fully developed nonlinear solutions are either time-dependent modes that oscillate slightly in the amplitude or time independent stable two-dimensional nonlinear waves with large amplitude referred to as 'permanent waves'. The results show that the shape and the amplitude of the nonlinear waves are strongly influenced by the permeability of the porous medium and the shear-thinning rheology. � 2010 Elsevier B.V.

The Trapped Vortex Combustor (TVC) is a new design concept in which cavities are designed to trap a vortex flow structure established through the use of driver air jets located along the cavity walls. TVC offers many advantages when compared to conventional swirl-stabilised combustors. In the present work, numerical investigation of cold flow (non-reacting) through the two-cavity trapped vortex combustor is performed. The numerical simulation involves passive flow through the two-cavity TVC to obtain an optimum cavity size to trap stable vortices inside the second cavity and to observe the characteristics of the two cavity TVC. From the flow attributes, it is inferred that vortex stability is achieved by circulation and the vortex is trapped inside when a second afterbody is added.The Trapped Vortex Combustor (TVC) is a new design concept in which cavities are designed to trap a vortex flow structure established through the use of driver air jets located along the cavity walls. TVC offers many advantages when compared to conventional swirl-stabilised combustors. In the present work, numerical investigation of cold flow (non-reacting) through the two-cavity trapped vortex combustor is performed. The numerical simulation involves passive flow through the two-cavity TVC to obtain an optimum cavity size to trap stable vortices inside the second cavity and to observe the characteristics of the two cavity TVC. From the flow attributes, it is inferred that vortex stability is achieved by circulation and the vortex is trapped inside when a second afterbody is added.The Trapped Vortex Combustor (TVC) is a new design concept in which cavities are designed to trap a vortex flow structure established through the use of driver air jets located along the cavity walls. TVC offers many advantages when compared to conventional swirl-stabilised combustors. In the present work, numerical investigation of cold flow (non-reacting) through the two-cavity trapped vortex combustor is performed. The numerical simulation involves passive flow through the two-cavity TVC to obtain an optimum cavity size to trap stable vortices inside the second cavity and to observe the characteristics of the two cavity TVC. From the flow attributes, it is inferred that vortex stability is achieved by circulation and the vortex is trapped inside when a second afterbody is added.

The objective of reservoir engineering is to optimize hydrocarbon recovery. One of the most common and efficient recovery processes is water injection. The water is pumped into the reservoir in injection wells in order to push the oil trapped in the porous media towards the production wells. The movement of the water front depends on the reservoir characteristics. To avoid an early water breakthrough in the oil production wells, a good knowledge of the subsurface is imperative. The properties of the rock, e.g. porosity and permeability, are therefore important for oil extraction since they influence the ability of fluids to flow through the reservoir. They represent unknown parameters that need to be estimated when simulating a reservoir. In this paper the authors are concerned with estimating the permeability field of a reservoir. To characterise the fluid flow into the reservoir we use a two phase (oil-water) 2D °ow model which can be represented as a system of coupled nonlinear partial differential equations which cannot be solved analytically. Consequently, we build a state- space model for the reservoir. There are many ways of representing state-space models, one of the most common being the Kalman Filter (KF) model and its variants, e.g. En(semble)KF. A more general representation is a dynamic Bayesian network. Recently, the performance of the EnKF and that of a non-parametric BN were investigated and compared in a twin experiment for permeability estimation [1]. The NPBN approach proved a promising alternative to the EnKF. Yet a fair number of open questions emerged from the comparison of the two methods. Moreover, in all investigations the assumptions of the EnKF method were used in the NPBN approach for a proper comparison. In this paper we try to answer some of the questions left open, and extend the initial work by making more realistic assumptions. Copyright © (2012) by IAPSAM & ESRA.

Experiments were conducted on the flow through a transonic turbine cascade. Secondary flows and a wide range of vortex types were encountered, including horseshoe vortices, shock-induced passage vortices, and streamwise vortices on the suction surface. In the separation region on the suction surface, a large rollup of passage vorticity occurred. The blunt leading edge gave rise to strong horseshoe vortices and secondary flows. The suction surface had a strong convex curvature over the forward portion and was quite flat further downstream. Surface flow visualization was performed and this convex surface displayed coherent streamwise vorticity. At subsonic speeds, strong von Kármán vortex shedding resulted in a substantial base pressure deficit. For these conditions, time-resolved measurements were made of the Eckert-Weise energy separation in the blade wake. At transonic speeds, exotic shedding modes were observed. These phenomena all occurred in experiments on the flow around one particular turbine nozzle vane in a linear cascade. © 2012 J. P. Gostelow et al.

Ports are important nodal points that stimulate the US economy. This is particularly true of the Ports of Los Angeles and Long Beach (POLA/LB). Over 40% of all containers shipped to and out of the US flow through this two-port complex. The POLA/LB along with other port complexes face many challenges - including maximizing operational efficiency while simultaneously minimizing risk from catastrophes, including terrorism and other man-made or natural disaster events and minimizing environmental impacts. Often these challenges are at odds with one another - increasing one often comes at the expense of achieving the other. The DHS-funded Center for Risk and Economic Analysis of Terrorism Events (CREATE) is developing a port security risk management and resource allocation system (PortSec). PortSec will support both tactical day-to-day security decision-making and long-term strategic security planning. An initial PortSec prototype (1.0) that supports tactical day-to-day risk assessment and resource allocation is currently undergoing evaluation at POLA/LB. © 2010 IEEE. 264 269 Sponsors: IEEE Boston Section IEEE-USA IEEE Nuclear and Plasma Sciences Society IEEE Engineering in Medicine and Biology Society IEEE Women in Engineering Conference code: 83344 Cited By :5

The time evolution of a thin conducting liquid film flowing down a porous inclined substrate is investigated when an electric field acts normal to the substrate. It is assumed that the flow through the porous medium is governed by Darcy's law together with Beavers-Joseph condition. Under the assumption of small permeability relative to the thickness of the overlying fluid layer, the flow is decoupled from the filtration flow through the porous medium. A slip condition at the bottom is used to incorporate the effects of the permeability of the substrate. From the set of exact averaged equations derived using integral boundary method for the film thickness and for the flow rate, a nonlinear evolution equation for the film thickness is derived through a long-wave approximation. A linear stability analysis of the base flow is performed and the critical Reynolds number is obtained. The results reveal that the substrate porosity in general destabilizes the liquid film flow and the presence of the electric field enhances this destabilizing effect. A weakly nonlinear stability analysis divulges the existence of supercritical stable and subcritical unstable zones in the wave number/Reynolds number parameter space and the results demonstrate how the neutral curves change as the intensity of the electric filed or the permeability of the porous medium is varied. The numerical solution of the nonlinear evolution equation in a periodic domain reveals that the base flow yields to surface structures that are either time independent waves of permanent form that propagate or time-dependent modes that oscillate slightly in the amplitude. Further, it is observed that the shape and amplitude of long-time waveforms are influenced by the permeability of the porous medium as well as by the applied electric field. The results reveal that the destabilization induced by the electric field in an otherwise stable film over a porous medium is exhibited in the form of traveling waves of finite amplitude. The presence of the porous substrate promotes the oscillatory behavior of the long-time waveform; however, the electric field has a tendency to suppress this oscillatory behavior. � 2010 The American Physical Society.

PurposeThe purpose of this paper is to develop an indigenous three‐dimensional computational code and apply it to compare flow and heat transfer characteristics for inline and staggered arrangement of circular tubes in a tube bundle.Design/methodology/approachA finite‐volume based computational code is developed to solve the momentum and energy equations for flow through a three‐dimensional rectangular channel and past built‐in tube bundles having inline and staggered arrangement. The approach is based on SIMPLE algorithm. The basic conservation equations of mass, momentum and energy are solved over a body‐fitting grid on the physical domain to obtain the flow and temperature fields.FindingsHeat transfer and pressure drop are compared for inline and staggered tube arrangements in a tube bundle over range of Reynolds numbers 300 ≤ Re ≤ 800. Results are validated suitably against those available in literature.Research implicationsTube‐fin heat exchangers with continuous fins on a tube array are commonly used in air‐conditioning industry and in air‐cooled condensers of power plants. The flow structure within the finned tube bank is complex due to the presence of a circular tube, which causes flow acceleration over the fin surface and flow separation on the back side of the tube resulting in low velocity wake region. The present study provides a better understanding of flow behavior and heat transfer for inline and staggered arrangement of tube bundles in tube‐fin heat exchangers at different Reynolds numbers.Originality/valueA numerical code based on finite volume method has been developed and used for computations to predict heat transfer and pressure drop characteristics for flow past inline and staggered arrangement of circular tubes. Predictions are made from the computed results about suitability of staggered/inline tube arrangements in a given range of Reynolds number.

Since its inception in 1996, the CO2 injection operation at Sleipner has been monitored by 3D time-lapse seismic surveys. Striking images of the CO2 plume have been obtained, showing a multi-tier feature of high reflectivity, interpreted as arising from a number of thin layers of CO2 trapped beneath thin, intra-reservoir mudstones. The topmost layer of the CO2 plume can be characterized most accurately, and its rate of growth quantified. From this the CO2 flux arriving at the reservoir top can be estimated. This is mostly controlled by pathway flow through the intra-reservoir mudstones. Flow has increased steadily with time suggesting that pathway transmissivities are increasing with time, and/or the pathways are becoming more numerous. Detailed 3D history-matching of the topmost layer cannot easily reproduce the observed rate of lateral spreading. Very high reservoir permeabilities seem likely, possibly with a degree of anisotropy. Other modelling variables under investigation include topseal topography, the number of feeder pathways and CO2 properties. Detailed studies such as this will provide important constraints on longer-term predictive models of plume evolution. © 2009 Natural Environment Research Council.

Background Flowthrough pretreatment is capable of removing much higher quantities of hemicellulose and lignin from lignocellulosic biomass than batch pretreatment performed at otherwise similar conditions. Comparison of these two pretreatment configurations for sugar yields and lignin removal can provide insights into lignocellulosic biomass deconstruction. Therefore, we applied liquid hot water (LHW) and extremely dilute acid (EDA, 0.05%) flowthrough and batch pretreatments of poplar at two temperatures and the same pretreatment severity for the solids. Composition of solids, sugar mass distribution with pretreatment, sugar yields, and lignin removal from pretreatment and enzymatic hydrolysis were measured. Results Flowthrough aqueous pretreatment of poplar showed between 63 and 69% lignin removal at both 140 and 180 °C, while batch pretreatments showed about 20 to 33% lignin removal at similar conditions. Extremely dilute acid slightly enhanced lignin removal from solids with flowthrough pretreatment at both pretreatment temperatures. However, extremely dilute acid batch pretreatment did realize greater than 70% xylan yields largely in the form of monomeric xylose. Close to 100% total sugar yields were measured from LHW and EDA flowthrough pretreatments and one batch EDA pretreatment at 180 °C. The high lignin removal by flowthrough pretreatment enhanced cellulose digestibility compared to batch pretreatment, consistent with lignin being a key contributor to biomass recalcitrance. Furthermore, solids from 180 °C flowthrough pretreatment were much more digestible than solids pretreated at 140 °C despite similar lignin and extensive hemicellulose removal. Conclusions Results with flowthrough pretreatment show that about 65–70% of the lignin is solubilized and removed before it can react further to form low solubility lignin rich fragments that deposit on the biomass surface in batch operations and hinder enzyme action. The leftover 30–35% lignin in poplar was a key player in biomass recalcitrance to enzymatic deconstruction and it might be more difficult to dislodge from biomass with lower temperature of pretreatment. These results also point to the possibility that hemicellulose removal is more important as an indicator of lignin disruption than in playing a direct role in reducing biomass recalcitrance. Electronic supplementary material The online version of this article (doi:10.1186/s13068-016-0660-5) contains supplementary material, which is available to authorized users.